High voltage transformer



Nov. 27, 1956 A. MEYERHANS EI'AL HIGH VOLTAGE TRANSFORMER Filed March 24, 1953 02. &

INVENTORS ATTORNEY to voltage waves having a steep front.

United States Patent HIGH VOLTAGE TRANSFORMER August Meyerhans, Nussbaumen, near Baden, and Martin Christotfel, Zurich, Switzerland, assignors to Aktiengesellschaft Brown, Boveri & Cie, Baden, Switzerland Application March 24, 1953, Serial No. 344,287

Claims priority, application Switzerland March 28, 1952 3 Claims. (Cl. 33670) The present invention relates to electrical transformer and other windings of the high voltage type and particularly those in which the windings may be subjected Unless some means are provided for distributing this voltage in a somewhat equal manner between the various coils which make up the windings and particularly those which constitute the primary i. e. the high voltage side of thetransformer, an extremely high stress is placed on those coils at the beginning of the primary winding which may result in a breakdown of the insulation thereon.

The pattern of voltage distribution between the various coils of the winding, i. e. the voltage gradient, is determined by their capacities and various expedients have been adopted to increase such capacities by the addition of other capacitative units thereby to improve the voltage gradient. One type of capacity unit in popular use consists of a conductive screen arranged to surround the outside of the high voltage winding and which is electrically connected to the beginning of the winding. However such screens require much space and result in constructions of undesirable shape. Moreover the edges of such screens must have high strength insulation since they carry the very high potential existing at the beginning of the primary winding, thus making it necessary to space the screens and winding far apart. The same disadvantage obtains when the additional capacity units are constituted by cylindrical metallic plates or the like imbedded in the transformer insulation or distributed throughout the length of the winding in a telescope like arrangement. That is, great difficulties arise because of the insulation requirement at the edges of the metallic insertions and because of the voltage gradients occurring due to the operational frequencies.

The object of the present invention is to provide an improved arrangement for high voltage windings such as the high voltage side of a transformer which results in a better voltage gradient in the event of steep front voltage waves. According to this inventive concept the high voltage side of the transformer is constituted by a plurality of series connected disc type coils in superposed relation and conductive and non-magnetic rings are disposed at both the inner and outer sides of the coils, the rings at each side being arranged in close superposed relation and each ring being insulated from the other rings. Preferably those rings at the inner sides of the coils overlap, i. e. capacitatively bridge such adjacent coils as are electrically connected together at their outer sides, and in a similar manner those rings at the outer sides of the coils capacitatively bridge such adjacent coils as are electrically connected together at their inner sides. Also those rings disposed at the inner and outer sides of the particular coil which constitutes the beginning of the winding are preferably connected to such coil at its point of connection to the high voltage source.

The inventive concept will be more clearly understood from the following detailed description and drawings wherein Fig. 1 is a view in central vertical section of a 2,772,403 Patented Nov. 27, 1956 portion of a transformer incorporating the invention and Fig. 2 is an electrical schematic view showing a slight modification.

With reference now to Fig. 1 wherein those portions of the transformer structure not essential to an understanding of the present invention have been omitted in the interest of simplifying the disclosure, it will be seen that the transformer is of the well known concentric winding type. The secondary or low voltage winding, sectionalized into two concentric, radially spaced coils 1a, 1b, is located adjacent to and concentric with the central core 2. Surrounding secondary windings 1a, 1b and separating the same from the high voltage primary winding 4 is a cylinder of insulation 3 of the well known laminated type made from paper. It will be observed that primary winding 4 is composed of a plurality of disc type coils 4a, 4b, 4c, 4d, 4e, and 4f arranged in superposed parallel spaced relation concentric with secondary windings 1a, 1b and that the several coils are interconnected in series, the connection between adjacent coils being located alternately at the inner and outer sides of the coils. Thus conductor 5a connects coils 4a and 4b at their outer sides, conductor 5b connects coils 4b and 40 at their inner sides, conductor 50 connects coils 4c and 4d at their outer sides, conductor 5d connects coils 4d and 42 at their inner sides and conductor 52 connects coils 4e and 4] at their outer sides. The turns which make up each coil have radial spacing therebetween but this is immaterial so far as the invention is concerned. The lead-in 6 from the high voltage source is connected to the inner side of coil 4a.

Metallic conductive and non-magnetic rings 7a, 7b, 7c and 7d are located between insulating cylinder 3 and the inner sides of the primary coils 411-41. These rings are each wrapped with insulating material 10 to insulate each from the other and are also arranged concentric with the axis of transformer core 2 and in close superposed relation. Preferably ring 7a overlaps, i. e. capacitatively bridges the vertical gap between the inner sides of primary coils 4a, 4b which are interconnected at their outer sides. In a similar manner, ring 7b capacitatively bridges primary coils 4c, 4d and ring 70 capacitatively bridges coils 42, 4f.

Another group of metallic conductive mutually insulated and non-magnetic rings 8a, 8b, 8c and 8d similar to rings 7a-7d are disposed adjacent the outer sides of primary coils 4a-4f. Ring 8b capacitatively bridges the vertical gap between the outer sides of primary coils 4b, 40 which are interconnected at their inner sides. In a similar manner, ring 8c capacitatively bridges coils 4d, 4e also interconnected at their inner sides.

If desired, rings 7a7d and 8a-8d instead of being metallic throughout may be constructed from laminated paper insulation which is then surface coated with a conductive material to bring about the desired capacity effect.

In order to obtain the desired alternate bridging efiect it will be seen that the height of the several rings 7a-7d and 8a8d is made greater than the combined height of each pair of adjacent primary coils so that abutment between adjacent rings occurs adjacent the connecting conductors 5a-5e for adjacent coils. This of course means that the uppermost inner ring 7a can be of full height but the uppermost outer ring 8a must be of half that height. Rings 7a and 8a, disposed at the inner and outer sides respectively of the uppermost coil 4a to an end terminal of which the high voltage lead 6 is connected, are also preferably interconnected by conductor 9 and are also connected to the lead 6.

It will be understood of course that the complete transformer includes other primary coils below those illustrated and that other capacitative coupling rings are associated therewith in the same manner as those already described to the end that the rings will be substantially coextensive in height with the entire length of the primary winding.

: Fig.1 Zshowsin schematiclfiorgn a slightly d fferent emvbOdirnent-of theinventionwherein-tthe hightvoltage lead 6' instead of being connected to the uppermost coilida' is connected to :an end terminal of one of: the inter-mediate .coils such as 4h thus dividingtheprima-rywinding in two electrically parallel branches,.one branch consisting .of coils- 4a 4h ,and the other coils. lh4p'. Other .wise .the arrangement of thelow vvoltage winding. la,

1b, core 2 and inner and outer auxiliaryrcapa'city rings a In conclusionit will ,be seen that theimproved. ar-

rangement" according tothe invention resultsin amost .cornpact construction and almost favorable voltage, dis ftribution along the entireprimary winding. -Moreover the, voltage difference between adjacent vcoilsflat :their non-connected. sidesis considerably reduced so-that the desired-protection of the transformer windings against damage from high voltage wavefronts is attained. The f invention is also applicable without difiicultyto high t voltage windings of other apparatussuch .as choke coils.

' We claim:

1. In a transformer of the concentric winding'type, a highvoltage winding comprising a plurality of disc-type coils arranged concentrically in superposed relation and connection in series to a high voltage lead-inand, to form groups of coils, the connections between adjacent :coils of the groups being made alternately at thejradially inner and outer sides of the coils, and a plurality of nonmagn'etic electrically conductiveri'ngs arranged'in'r'elatively close superposed relation at both the inner and outer sides of said coils, said rings being insulated each from the other and being of such length along the axis of said high voltage Winding as to capacitatively bridge adjacent coilsat that inner and outer side ofsaid high voltage winding at which said series-connected coils are without connection.

the. high :voltage lead-in to said high voltage winding is connected to an end. terminal ofz-an intermediate one of .said plurality of superposed disc' type coils thereby'to establish two branches in parallel extending in opposite directiomfrom said. intermediate coil.

References Cited in the file of this patent UNITED STATES PATENTS Re. 14,473 Fortescue May 21, 1918 1,062,046 Smith May 20,1913 2,220,539 Panov et a1. Nov. 5, 1940 2,295,371 Vogel SeptpS, 1942 a if 

